: This application is for a "Mentored Patient-Oriented Research Career Development Award" (K23) to study treatment adherence in co-occurring psychiatric and drug use disorders (COD), under the mentorship of Bruce J. Rounsaville, M.D. and Richard S. Schottenfeld, M.D. Nonadherence is a critical issue in COD, especially among those with depressive disorders, as it occurs frequently and limits the maximal benefit achieved by efficacious treatments, particularly those with the potential to improve both conditions (e.g., antidepressants). Therefore, adherence-enhancing interventions for COD can optimize the efficacy of treatments. They are also adaptable to new treatments that are being developed. While preliminary studies indicate that adherence-enhancing interventions are efficacious for patients with non-COD, little systematic evaluation has occurred in COD. Compared to developing new contents for treatment, studying brief strategies to improve adherence to existing treatments is a highly cost-efficient approach that can have a large and rapid payoff. The research plan for this K23 application entails: 1) the evaluation of adherence issues in 9 ongoing studies and 2) completion of a new clinical trial evaluating innovative adherence-enhancing methods for COD in a dual-diagnosis outpatient clinic. This new clinical trial will employ a dismantling design, within which 75 outpatients with co-occurring depressive disorders and drug abuse/dependence (CODDA) will be randomly assigned to: 1) Treatment-as-Usual (TAU), a control condition offering medication management, standard education regarding diagnosis and the importance of adherence, and group counseling, 2) TAU+Adherence Feedback (TAU+AF), in which patients receive TAU plus computerized feedback on medication and counseling adherence, based on Medication Event Monitoring System (MEMS; Aprex Corporation, Fremont, CA) data and attendance records, or 3) TAU+Motivationally Enhanced Feedback (TAU+MEF), in which TAU plus Motivational Enhancement Therapy and Contingency Management will be added to AF. Primary outcome measures are: 1) rates of adherence to antidepressant medication, as measured by MEMS caps and self-report, 2) rates of counseling attendance, and 3) reductions in illicit drug use, including achievement of abstinence, as assessed by twice-weekly urine toxicology tests and self-report. Secondary outcomes include reductions in depressive symptomatology and rates of re-hospitalization.